Evaluation of the grain methionine, lysine and tryptophan contents of maize ( Zea mays L.) germplasm in the Germplasm Enhancement of Maize Project

Abstract

The Germplasm Enhancement of Maize (GEM) Project is a cooperative effort between the USDA-ARS, private industry and public researchers to broaden and enhance the germplasm base of maize. In this program, selected accessions from the Latin American Maize Project, and seven tropical hybrids donated by DeKalb to the GEM Project, were crossed to elite proprietary inbred lines contributed by commercial plant breeding programs. In most cases, the resulting hybrids were crossed to a second commercial inbred line and the resulting 25% exotic hybrids were used as breeding populations for further development. To identify GEM germplasm with value to protein quality breeding programs, we developed a process for evaluating the content of the essential amino acids methionine, lysine and tryptophan in the grain of GEM germplasm that balances the need for multiple-year evaluations with the constantly changing entry list of this germplasm screening program. This process involves annual field trials with common checks. Weak entries are dropped from the trial each year to make room for new entries, while strong entries are retained. Methionine exhibited the most significant variation, followed by lysine and then tryptophan. A number of GEM lines had methionine or lysine levels that were significantly better than Corn Belt checks and some were competitive with high-amino acid checks.

Diversity of Maize Kernels from a Breeding Program for Protein Quality: II. Correlatively Expressed Functional Amino Acids

“…The three amino acid contents, at least in this germplasm, may have the power to differentiate between opaque and translucent endosperm textures as supported by large percentage of correct classification of opaque and translucent populations (Fig. 1); however, this level of differentiation may be modified by the genetic background (Table 4) that was reported for exotic germplasm (Scott and Blanco, 2009) and commercial maize genetic resources in the United States (Singh et al, 2011).…”

“…However, the increase in LYS was not large enough to counterbalance increases in MET and CYS in all HGEs, except SSO, in which MET and CYS were negatively correlated with their respective relative contents, and all three amino acids were negatively correlated with CLR. 5) and other studies (Scott and Blanco, 2009), was not reduced because of increased LYS (Newell et al, 2014). Notwithstanding the small Q 2 for BCM-pr (14.0%) as compared with BCM (47.0%), phytochemicals other than protein may have contributed to LYS determination in SSO.…”

“…However, the first indication of a slight departure from close relationships between opaque and translucent families due to HG and inbreeding effects were evident at the family and accession level (e.g., decreasing matrix mean r values between P1 of T-OP and P2 each of T-S1, T-S2, and T-S3 in AR16021-B73; and between O-S1 and each of O-S2 and O-S3 in Nokomis Gold; Table 4). 1); however, this level of differentiation may be modified by the genetic background ( Table 4) that was reported for exotic germplasm (Scott and Blanco, 2009) and commercial maize genetic resources in the United States (Singh et al, 2011). 1); however, this level of differentiation may be modified by the genetic background ( Table 4) that was reported for exotic germplasm (Scott and Blanco, 2009) and commercial maize genetic resources in the United States (Singh et al, 2011).…”

“…Depending on its tropical or subtropical origin and whether it is yellow flint, medium flint, or medium yellow dent, kernels of QPM maize, which combined the opaque-2 genes with genetic modifiers, contained high levels of LYS (4.1 to 4.5 as compared with 1.6 to 2.6 g 100 g -1 protein in normal maize varieties) and had highdensity, translucent endosperm and appearance similar to normal maize (Prasanna et al, 2001;Scott et al, 2004). The germplasm enhancement of maize project (GEM) program (Pollak, 2003;Scott and Blanco, 2009) developed maize lines with significantly better MET and LYS contents than Corn Belt checks, and some were competitive with high-amino acid checks. For example, the dzr1 mutation that resulted in increased MET content has been used to develop inbred lines with improved kernel MET content (Olsen et al, 2003).…”

“…Land used for all trials was organically certified with the exception of the small MFAI nursery, and organic management was applied to all nurseries in 2008. Seed of well-filled ears was hand-harvested and dried (Rosales et al, 2011) and were attributed to a pleiotropic effect of the o2 mutation (Scott and Blanco, 2009). Maize breeding programs have been successful in overcoming some of the poor agronomic traits, including the use of modifier genes to make the endosperm more vitreous, and in developing QPM lines adapted to, and potentially valuable for animal feed that found commercial use in, some parts of the world (Prasanna et al, 2001) but not in the Corn Belt of the United States .…”